Method and apparatus for printing coded media

ABSTRACT

A method and apparatus for printing at least first and second indicia on a record medium. The apparatus includes a print station to which the medium is incrementally fed. The print station uses a thermally operated print head having a plurality of separately energizable resistive elements which heat up, when energized, to print a &#39;&#39;&#39;&#39;colored&#39;&#39;&#39;&#39; bar code on the medium, which may be a label. A shiftable carriage member supplies first and second heat-activatable &#39;&#39;&#39;&#39;color ribbons&#39;&#39;&#39;&#39; to the print station. When the first ribbon is at the print station, the print head and the medium are pressured together with the first ribbon therebetween, and selected ones of the resistive elements are energized to transfer the first color to the medium. The medium is then held stationary while the first ribbon is removed and the second color ribbon is shifted by the carriage member to the print station. The print head and the medium are then pressured together with the second ribbon therebetween, and selected ones of the resistive elements are energized to transfer the second color to the medium.

United States Patent 91 Combs [54] METHOD AND APPARATUS FOR PRINTING CODED MEDIA [75] Inventor: Ollah Combs, Morrow, Ohio [73] Assignee: The National Cash Register Company, Dayton, Ohio 22 Filed: Sept. 21, 1970 21 App]. 190.; 73,699

[52] U.S. Cl. ..101/21, 101/193, 346/76, 101/27, 197/156 [51] Int. Cl ..B4lj 7/54, B4lf l/44, B4lm 5/20 [58] Field of Search ..10l/27,21,9, 10, 101/11, 30, 193; 197/156; 346/76 [56] References Cited UNITED STATES PATENTS 933,186 9/1909 Latta ..197/156 1,030,500 6/1912 Brown ..197/156 2,065,690 12/1936 Gould et a1. ..101/27 X 3,004,486 10/1961 Typrowicz ..101 193 3,217,638 11/1965 Gottscho ..101/27 3,289,573 12/1966 Apicella ..l0l/27 3,430,557 3/1969 Peters ..101/27 3,432,022 3/1969 Priebs ..197/153 1 Apr. 10, 1973 Primary Examiner-William B. Penn Attorney-Louis A. Kline, Albert L. Sessler, Jr. and Elmer Wargo [5 7] ABSTRACT A method and apparatus for printing at least first and second indicia on a record medium. The apparatus includes a print station to which the medium is incrementally fed. The print station uses a thermally operated print head having a plurality of separately energizable resistive elements which heat up, when energized, to print a colored bar code on the medium, which may be a label. A shiftable carriage member supplies first and second heat-activatable color ribbons to the print station. When the first ribbon is at the print station, the print head and the medium are pressured together with the first ribbon therebetween, and selected ones of the resistive elements are energized to transfer the first color to the medium. The medium is then held stationary while the first ribbon is removed and the second color ribbon is shifted by the carriage-member to the print station. The print head and the medium are then pressured together with the second ribbon therebetween, and selected ones of the resistive elements are energized to transfer the second color to the medium.

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PULSER POWER SOURCE INVENTOR METHOD AND APPARATUS FOR PRINTING CODED MEDIA BACKGROUND OF THE INVENTION:

This invention relates to a method and apparatus for printing at least first and second indicia on a record medium through the use of a thermally operated print head and first and second heat-activatable ribbons. In recent times, there has been an increased effort to use tags or labels which are coded to provide data to input terminal devices instead of manually entering the data on an input device like a cash register. The labels contain data about the items to which they are attached and are used, for example, in retailing and inventorying functions and the like. The data which is coded on the label may take the form of parallel color bars which appear on the label according'to a predetermined code. One such coded color label is disclosed in the United States patent application of John B. Christie, Ser. No. 837,850, which was filed on June 30, 1969, and is assigned to the same assignee as this application.

The present invention provides a low-cost method and apparatus for printing coded labels.

SUMMARY OF THE INVENTION:

This invention relates to a method and apparatus for printing at least first and second indicia on a record medium. The apparatus includes a print station and a feed means for incrementally feeding the medium to the print station. The print station includes a thermally operated print head having a plurality of separately energizable resistive elements adapted to be heated when energized. A carriage means at the print station is shiftable to first and second positions relative to the print head, and first and second ribbon supply means are mounted on the carriage means for supplying first and second indicia to the medium. When printing of the first indicium is to be effected, the carriage means is shifted to the first position, and a platen is used to force the medium against the print head with a ribbon of the first ribbon supply means being positioned therebetween. Selected ones of the resistive elements are then energized, enabling the first indicium to be formed on the record medium. The platen is moved away from the print head, enabling the carriage means to be shifted to the second position, which shifting removes the first ribbon and positions a ribbon of the second ribbon supply means between the platen and the print head. The medium is held stationary during the shifting of ribbons; and, when the platen is again moved towards the print head, the' second ribbon is positioned therebetween. Selected ones of the resistive elements are then energized, enabling the second indicium to be printed on the medium. The background of the medium may be used to obtain a third indicium by not printing either of the first or second indicia on selected areas of the medium.

BRIEF DESCRIPTION OF THE DRAWINGS:

FIG. 1 is an elevational view of the apparatus of this invention showing the means for feeding a record medium to a print station where first and second indicia are printed on the medium by use of a thermally operated print head.

FIG. 2 is an enlarged, side-elevational view, partly in cross-section, and is taken along the line 2-2 of FIG. 1 to show additional details of the first and second indicia and the means for moving them in operative positions relative to the print station.

FIG. 3 is an enlarged, side-elevational view, partly in cross-section, and is taken along the line 33 of FIG. 1 to show a drive means for incrementally moving the first and second indicia to the print station.

FIG. 4 is a front elevational view of the drive means shown in FIG. 3 as viewed from the left side of FIG. 3 to show additional details thereof.

FIG. 5 is an enlarged plan view of a thermally operated print head used at the print station.

FIG. 6 is a cross-sectional view of the thermally operated print head at the print station and is taken along the line 6-6 of FIG. 5.

FIG. 7 is a general schematic diagram of control means which may be used in this invention.

FIG. 8 is a portion of the medium which is separated into an individual label, showing a finished product from the printing operation having first and second colors printed thereon, the background of the label providing a third color for the code used in printing.

DETAILED DESCRIPTION OF THE INVENTION:

The general arrangement of the various elements of the printer apparatus of this invention is shown in FIG. 1. The apparatus, designated generally as 20, is supported upon a base 22 and a vertical support wall 24 upstanding therefrom. A record medium 26, supplied by a supply reel 28, is incrementally driven to a print station 30 by a conventional capstan 32 and pinch roller 34.

The print station 30 includes a thermally operated print head, designated generally as 36, and a movable platen 38, which are spaced apart in the inoperative position shown in FIG. 1. A clamp member is located on each side of the print station to hold the record medium 26 stationary during the printing operation. A first clamp member, including a stationary member 40 and a solenoid-operated movable platen 42, is shown clamping the medium 26. A second clamp member, shown downstream of the print station 30, also includes a stationary member 44 and a solenoid-operated movable platen 46 and is shown clamping the medium 26. A carriage means, designated generally as 48, is located generally beneath the print station 30 and is used to feed first and second thermally activated colored ribbons to the print station to effect the printing on the medium 26 in cooperation with the thermally operated print head 36. In the specific embodiment described, the apparatus 20 is used to print green and black parallel stripes of color on the medium 26, which has a white background. Details of the various elements included in the apparatus will follow.

The record medium 26, supplied by the reel 28, consists of a tape which is perforated as at 50, as shown in FIG. 2, to provide a plurality of labels which may be easily separated from one another. One such label having coded printing thereon is shown in FIG. 8. The medium 26 to be printed upon is stored on the reel 28 (FIG. 1) until it is advanced to the print station 30 by the capstan 32 and pinch roller 34, which feed the tape an incremental amount equal to the length of one in- I in a slot 58 in the wall 24. A tension spring 60, having one end secured to a pin in the wall 24 and the remaining end secured to the pin 56, is used to rotate the arm 52 clockwise about the pin 54, as viewed in FIG. 1. A flanged roller 62 is rotatably mounted on the free end of the arm 52, and the medium 26 is routed around the roller.

Conventional limit switches, shown only diagrammatically as 64 and 66 (FIG. 1) are used to control the unwinding of the medium 26 from the reel 28. The reel 28 has associated with it a conventional slip clutch (not shown), which maintains a pre-set torque on the reel to restrain it from turning in the direction of the arrow marked 68. As the medium 26 is moved from left to right (as viewed in FIG. 1) past the print station 30, the reel 28 is held stationary by the slip clutch mentioned, and the arm 52 rotates counter-clockwise to the position shown in phantom outline as 70. When the arm 52 reaches the position shown as 70, it actuates the limit switch 64, causing a motor (not shown) to rotate the reel in the direction of the arrow 68 (overriding the pre-set clutch), which rotation unwinds the medium 26 from the reel 28. As the medium 26 unwinds, the arm 52 is pulled clockwise by the spring 60 (to take up the slack of the unwinding medium 26) until it reaches the extreme position shown to the left in FIG. 1, at which time the limit switch 66 is actuated to shut off the motor rotating the reel 28.

The carriage means 48 for feeding the first and second thermally activated colored ribbons to the print station 30 to effect printing on the medium 26 in cooperation with the thermally operated print head 36 is shown in detail in FIGS. 1, 2, 3, and 4. The carriage means 48 includes a frame 71, which is slidably mounted on a plurality of pins 72, which are perpendicularly secured to the vertical wall 24. A camming means 74 (FIG. 2) is used to movethe frame 71 of the carriage means 48 parallel to the wall 24. When the carriage means 48 is in the first position, shown in FIG. 2, the first ribbon 76 is positioned between the print head 36 and the platen 38. When the carriage means 48 is moved to the second position (by the camming means 74), the second ribbon 78 will be shifted to the left (as viewed in FIG. 2) and thereby occupy the printing position beneath the platen 38. Because both ribbons 76 and 78 are mounted together on the frame 71, the first ribbon 76 naturally moves to the left of the platen 38 (to occupy the position shown in phantom outline 80) when the carriage means 48 is moved to the second position.

The carriage means 48 is moved between the first and second positions by the camming means 74 shown in FIGS. 1 and 2. The camming means 74 includes a first cylindrical cam member 82 having one end which is fixed to the frame 71 and the remaining end cut at an angle of approximately 45. The member 82 is free to move axially on a shaft 84; however, the member 82 is restrained from rotation thereon by a spring-loaded pin 86, which is secured in the wall 24 and depends into an axially aligned slot 88 located on the periphery of the member 82. The camming means also includes a second cylindrical camming member 90, which is cut at one end at an angle, as at 92, to complement the angle on the member 82. The other end of the member 90 is cut perpendicularly to its axis of rotation and is secured to one end of a lever 94 to be rotated on the shaft 84 when the lever 94 is rotated in either direction. The shaft 84 is conventionally restrained against axial movement in the wall- 24. The remaining end of the lever 94 is pivotally joined to the operating plunger 96 of a solenoid 98 (FIG. 1), which is secured to the wall 24. A tension spring 100 (FIG. 1), having one end secured to the plunger 96 and the other'end secured to the wall 24, is used to return the lever 94 to the position shown in FIGS. 1 and 2, in which the carriage means 48 is in the first position shown. When the solenoid 98 is energized, its plunger 96 is withdrawn, and the lever 94 is rotated counter-clockwise (as viewed in FIG. 1 and the second camming member 90 is rotated thereby to force the first camming member 82 to move axially on the shaft 84 (to the left as viewed in FIG. 2) to move the carriage means 48 to the left to the second position. in which the second ribbon 78 is positioned under the platen 38. When the solenoid 98 is deenergized, the tension spring 100 pulls the lever 94 clockwise (as viewed in FIG. 1) to restore the carriage means 48 to the first position with the assistance of springs like 102 (FIG. 2). Suitable, adjustable, limit stops (not shown) on the solenoid plunger 96 controlv the length of travel of the lever 94, so as to accurately control the movement of the carriage means 48 between the first and second positions.

The first and second ribbons are mounted on the carriage means 48 (FIG. 2) for incremental feeding to the print station 30. The first ribbon 76 is fed from a supply reel 104 rotatably mounted on a shaft 105 (FIG. 1) and is routed over the idler rollers 106 and 108, which are rotatably mounted on pins 110 and 112, respectively, which are perpendicularly mounted on the frame 71. While positioned between the rollers 106 and 108, the ribbon 76 is positioned parallel to the platen 38 and the print head 36. From the roller 108, the ribbon 76 is routed to a take-up reel 1 14 (FIG. 2), which is keyed to a shaft 1 16, which is rotatably mounted in the frame 71 and perpendicular thereto. A lever 118 is rotatably mounted on the shaft 116 and is used to incrementally rotate the shaft 116, to which the reel 114 is secured. A driving pawl means 120 (FIG. 4) is mounted on the lever 118 and includes a driving pawl 122, which has one end pivotally mounted on the lever 118, and the remaining end has a tooth-engaging portion 124 to engage a toothed driving wheel 126. A spring 128 is used to keep the portion 124 in driving engagement with the wheel 126. The free end of the lever 118 is pivotally joined to the free end of the operating plunger 130 of a solenoid 132. When the solenoid 132 is energized, the plunger 130 is withdrawn, and the lever 118 is rotated clockwise (as viewed in FIG. 4) on the shaft 116. As the lever 118 rotates, it carries the pawl 122 therewith to thereby rotate the toothed wheel 126 clockwise, which incrementally rotates the shaft 116 and the takeup reel 114 clockwise. Conventional limit stops (not shown), in cooperative association with the operating plunger 130, control the extent of incremental feed of the ribbon to the print station 30. A tension-type restoring spring 134 is used to return the plunger 130 and the lever 118 to the inoperative position, shown in FIG. 4. An anti-back'up pawl 136 has one end which is pivotally mounted on the frame 71, and the other end engages the teeth on the toothed wheel 126. During the time when the toothed wheel 126 is driven by the pawl 122, the pawl 136 rides up a tooth and engages the next succeeding tooth (to prevent back-up) when the driving pawl 122 has rotated the wheel 126 an incremental amount equivalent to one tooth. A spring 138 resiliently urges the pawl 136 into the toothed wheel 126. As the solenoid 132 is energized, the ribbon 76 is wound up on the take-up reel 114 (FIG. 2) to present an unused area of ribbon to the print station 30. In a similar manner, the second ribbon 78 is fed from a supply reel 140 (located behind the reel 104 in FIG. 1), is routed over the rollers 106 and 108, and is taken up on a take-up reel 142 (FIG. 2). Because the reel 142 is also keyed to the shaft 116, it is incrementally rotated an amount equal to that of the reel 114, and both ribbons 76 and 78 are fed to the print station 30 each time the solenoid 132 is energized.

Each of the ribbons 76 and 78 includes a base having a transferable coating composition thereon. The coating composition generally comprises about 3 percent to 40 percent, by weight, of an olefinic polymer; about 3 percent to 40 percent, by weight, of a wax; about percent to 70 percent, by weight, of a thermoplastic aminotriazine-sulfonamide-aldehyde resin; and about 1 percent to percent, by weight, of a sensible material which, in the embodiment described, is a coloring agent for the different colors used. A more detailed explanation of the method of making heat-activatable color ribbons may be found in U.S. Pat. application Ser. No. 35,230, filed on May 6, 1970, by Charles T. Fellows et al., for A Transfer Medium for Producing Scratch and Smudge Resistant Marks and a Process for Making the Same; see Example 15 of that application in particular. U.S. Pat. application Ser. No. 35,230, filed May 6, l970, is assigned to the same assignee as the present invention.

The print head 36, shown in FIGS. 5 and 6, is constructed in the following manner. The print head 36 is supported on an insulating substrate 144, which may be made of glass or other suitable material. A layer 146, of resistive material, like tantalum oxide, about 1,300 Angstroms thick, is deposited on the substrate 144 by conventional tantalum-vacuum deposition techniques. The layer 146 is then masked and conventionally etched to produce the pattern shown in FIG. 5. The pattern includes a common leg 148 having joined thereto the individual heating elements 150, with a separate energizing leg 152 for each element 150. A layer 154, of conductor material (like gold), is deposited on each leg 152, and a layer 156, of conductor material, is deposited on the common leg 148 to leave the heating element 150 uncovered (free of conductor material), as shown in FIG. 6. A thin layer 158, of glass (about 5,000 Angstroms thick), is then deposited over the heating elements 150 and portions of the layers 154 and 156 of conductor material, as shown in FIG. 6. The layer 158 affords protection to the heating elements from abrasion from the ribbons 76 and 78 when in contact therewith during the printing operation. The ribbons 76 and 78 are so positioned that their transferable coatings (like 76C in FIG. 6) face the medium 26. In the embodiment shown, each heating element has a length of about one half-inch and a width of about 0.013 inch. The elements 150 are placed in spaced parallel relationship on centers which are approximately 0.015 inch apart. Naturally, the specific dimensions selected for the elements 150 are dependent upon the particular print size desired. Each conducting leg 152 has its own energizing lead 160 connected thereto, as shown in FIGS. 5 and 6. These leads 160 are connected to a conventional switching network 162, which is connected to a conventional pulsed power source 164. The switching network simply selects the individual leads 160 to be energized to effect printing of the first and second colors in accordance with a particular code. As any conventional logic may be used for this purpose, any conventional circuitry may be used.

Because conventional control circuitry may be used, only a block diagram is shown in FIG. 7 for controlling the apparatus 20. The control means includes a conventional input device 166, like a keyboard, upon which the desired input data is entered. This data includes statistical data and the number of labels required, and is fed to a conventional control logic 168. Assume that a portion of the medium 26 to be printed upon is at the print station 30, and the carriage means 48 is in the first position. The control logic 168= will actuate a pair of solenoids 170 and 172 to move the platens 42 and 46 against their respective stationary members 40 and 44 to hold the medium 26 in a fixed position. A solenoid 174 is actuated by the control logic 168 for forcing the platen 38, the medium 26, and the first ribbon 76 into intimate contact with the print head 36. The particular heating elements 150 to be energized to print the color bars of the first color are energized by the control logic 168. When these energized elements 150 heat up, the color from the from the thermally activated first ribbon 76 is transferred to the medium 26 to produce the color bars shown in FIG. 8. For example, all the strips numbered 176 in FIG. 8 are produced from the first ribbon 76 in one printing operation. After printing of the first color from the first ribbon 76, the solenoid 174 is deenergized to permit the platen 38 to move away from the print head 36. During this time, the solenoids 170 and 172 remain energized to hold the medium 26 in place, as there is a tendency for the first ribbon 76 to stick to the medium 26 after the printing operation. Holding the medium 26 in place is also necessary to maintain very accurate registration of the printing of the color bars on the medium 26. The solenoid 98 of the camming means 74 is then energized by the control logic 168 to move the carriage means 48 into the second position, in which the second ribbon 78 is positioned at the print station 30. The solenoid 174 is then energized by the control logic 168 to force the medium 26 and the second ribbon 78 into intimate contact with the print head 36. Selected ones of the heating elements 150 are then energized to print the color bars of the second color. For example, the bars marked 178 in FIG. 8 are the bars which are printed by using the second ribbon 78. All of the bars 178 are printed at one time. The bars like 180 are the same color as the background of the medium 26 and are printed" by not energizing the corresponding heating elements 150 of the print head 36 during the printing of the first and second colors. By this arrangement, a three-color code is obtained on the medium. The width of the heating elements 150 is made narrower than the width of the color bar to be printed, due to the fact that some of the heat produced by a particular element will extend to areas of the medium adjacent to the element, causing a bleeding of color on the medium 26. This bleeding is utilized and results in a color bar of desired width, as shown in FIG. 8, with little overlapping or spacing between adjacent color bars.

After the color bars of the second ribbon 78 are printed on the medium shown in FIG. 8, the solenoid 174 is deenergized, allowing the platen 38 to return to the home position, shown in FIG. 1. The solenoid 98 is also deenergized by the control logic 168 (FIG. 7), allowing the carriage means 48 to be returned to the first position. The solenoids 170 and 172 are then deenergized by the control logic 168, enabling the platens 42 and 46 to be moved away from their associated members 40 and 44, respectively, enabling the medium 26 to be indexed or moved. The motor 182 (FIG. 7), associated with the capstan 32, is then energized by the control logic 168 to incrementally index the medium 26 (to the right as viewed in FIG. 1) an amount equivalent to one label, as shown in FIG. 8. A conventional sensing means 184 (shown only as a box in FIG. 1) is used to maintain synchronization of label feeding with the printing operation. For example, the sensing means 184 may be a photoelectric cell means which senses the notches on the edges of the medium 26 to insure that the motor 182 incrementally indexes the medium 26 so as to center the coded printing on an individual label. The solenoid 132 is then energized by the control logic 168 to simultaneously index both color ribbons 76 and 78 an incremental amount, so as to present an unused portion of the ribbons to the print station 30. The printing operation just described'is then repeated as many times as is necessary to obtain the desired number of labels.

What is claimed is:

1. An apparatus for printing at least first and second indicia on a medium comprising:

a print station; and

feed means for incrementally feeding the medium to said print station;

said print station including:

a single stationary print head having a plurality of separately-energizable resistive elements which have predetermined shapes and which become heated when selectively energized by a control means;

a carriage means having drive means for shifting it to first and second positions relative to said print head in response to said control means;

first and second supply means mounted on said carriage means for supplying first and second thermally responsive ribbons respectively to said print head;

a platen means and actuator means therefor for urging said medium against said first ribbon and print head when said carriage means is in said against said second ribbon and print head when said carriage means isshifted to said second posi; tion, enabling said second indicia to be formed on said medium when selected ones'of said resistive elements are energized by said control means;

said first and second indicia being formed on said medium in shapes corresponding to the shapes of the associated resistive elements; and

said resistive elements being the sole means for forming the shapes of said first and second indicia on said medium.

2. The apparatus as claimed in claim 1 further including clamping means located on opposite sides of said print station to hold said medium while said first and second indicia are formed thereon to control the registration of said first and second indicia on said medium.

3. The apparatus as claimed in claim 1 in which said resistive elements are positioned in aligned, equallyspaced, parallel relationship with one another and in which each said resistive element has a generally rectangular outline having a fixed width for its narrow dimension whereby said first and second indicia are formed on said medium in rectangular shapes corresponding to-the shapes of said resistive elements, and in which the fixed width of each said resistor element is less than the width of the corresponding rectangular shape produced thereby.

4. The apparatus as claimed in claim 3 in which said drive means shifts said carriage means at right angles to said medium when shifting said carriage means to said first and second positions and in which said first and second supply means simultaneously move said first and second ribbons a fixed incremental amount for each incremental feeding of said medium.

5. A method of printing at least first and second indicia in the form of parallel bars on a medium comprising the steps of: feeding the medium to a stationary print station including a stationary print head having a a plurality of separately energizable resistive elements which heat up when energized; bringing said medium and print head together with a thermally activatable first indicia member positioned thcrebetween; energizing selectedones of said resistive elements so as to activate said first indicia member and thereby transfer said first indicia to said medium; removing said first indicia member while holding the position of said medium fixed relative to said print head; bringing said medium andprint head together with thermally activatable second indicia member positioned therebetween; and energizing selected ones of said resistive elements so as to activate said second indicia member and thereby transfer said second indicia to said medium. 

1. An apparatus for printing at least first and second indicia on a medium comprising: a print station; and feed means for incrementally feeding the medium to said print station; said print station including: a single stationary print head having a plurality of separately-energizable resistive elements which have predetermined shapes and which become heated when selectively energized by a control means; a carriage means having drive means for shifting it to first and second positions relative to said print head in response to said control means; first and second supply means mounted on said carriage means for supplying first and second thermally responsive ribbons respectively to said print head; a platen means and actuator means therefor for urging said medium against said first ribbon and print head when said carriage means is in said first position, enabling said first indicia to be formed on said medium when selected ones of said resistive elements are energized by said control means, and for urging said medium against said second ribbon and print head when said carriage means isshifted to said second position, enabling said second indicia to be formed on said medium when selected ones of said resistive elements are energized by said control means; said first and second indicia being formed on said medium in shapes corresponding to the shapes of the associated resistive elements; and said resistive elements being the sole means for forming the shapes of said first and second indicia on said medium.
 2. The apparatus as claimed in claim 1 further including clamping means located on opposite sides of said print station to hold said medium while said first and second indicia are formed thereon to control the registration of said first and second indicia on said medium.
 3. The apparatus as claimed in claim 1 in which said resistive elements are positioned in aligned, equally-spaced, parallel relationship with one another and in which each said resistive element has a generally rectangular outline having a fixed width for its narrow dimension whereby said first and second indicia are formed on said medium in rectangular shapes corresponding to the shapes of said resistive elements, and in which the fixed width of each said resistor element is less than the width of the corresponding rectangular shape produced thereby.
 4. The apparatus as claimed in claim 3 in which said drive means shifts said carriage means at right angles to said medium when shifting said carriage means to said first and second positions and in which said first and second supply means simultaneously move said first and second ribbons a fixed incremental amount for each incremental feeding of said medium.
 5. A method of printing at least first and second indicia in the form of parallel bars on a medium comprising the steps of: feeding the medium to a stationary print station including a stationary print head having a plurality of separately energizable resistive elements which heat up when energized; bringing said medium and print head together with a thermally activatable first indicia member positioned therebetween; energizing selected ones of said resistive elements so as to activate said first indicia member and thereby transfer said first indicia to said medium; removing said first indicia member while holding the position of said medium fixed relative to said print head; bringing said medium and print heAd together with a thermally activatable second indicia member positioned therebetween; and energizing selected ones of said resistive elements so as to activate said second indicia member and thereby transfer said second indicia to said medium. 